Preseason Range-of-Motion and Motor-Performance Asymmetries in Elite Male Youth Soccer Players in Spain

CONTEXT: Side-to-side differences of lower limb range of motion and motor performance may predispose athletes to injury. Previous research has investigated side-to-side asymmetries among adult soccer players, but there is limited evidence for youth players particularly during preseason. The purpose of this study was to perform preseason side-to-side symmetry analyses using the anterior reach test, hip active internal (IR)/external rotation (ER), active knee extension (AKE), weight-bearing lunge test (WBLT), drop hop (DH), and single hop for distance. DESIGN: Cross-sectional study. METHODS: Sixty-nine male elite soccer players (age: 16.8 [0.9] y, height: 176.0 [6.8] cm, mass: 67.9 [6.4] kg) participated in the study. The anterior reach test, IR/ER, AKE, WBLT, DH, and single hop for distance tests were performed the first day of the preseason. The analysis included side-to-side group- (Bonferroni-corrected significance tests, effect sizes [Wilcoxon r]) and individual-level comparisons (absolute asymmetry [as percentage]). Limb symmetry indices were calculated and clinically significant absolute asymmetry defined (>10%). Clinically significant absolute asymmetry overall prevalence (as percentage) and side prevalence (as percentage) was computed for each measure. RESULTS: Side-to-side significant differences existed for hip IR (P = .005, Wilcoxon r = .40). The overall prevalence of clinically significant absolute asymmetries for anterior reach test, hip IR, hip ER, AKE, WBLT, DH, and single hop for distance was 20.3%, 66.7%, 37.7%, 71.0%, 39.1%, 36.2%, and 5.8%, respectively. CONCLUSIONS: Group-level analysis found statistically significant side-to-side differences in hip IR only. Individual-level analysis revealed many players had clinically significant asymmetries in hip IR, hip ER, AKE, WBLT, and DH reactive strength index.